Heat operated pumping system



Oct. 27, .1959 F. J. WENNERBERG 2,910,119"

- HEAT OPERATED PUMPING SYSTEM Filed Sept. 19, 1955 IN VEN T 0R 95112Johan h/rmwerg MWW ' ATTORIVE V tiebolaget Separator, Stockholm, Sweden,a corporation N i of Sweden Application September 19, B55, Serial No.535,174

1 Claim. (31. 159-2 -This invention relates to heat-operated pumpingsystems of the type having a liquid pump which directly utilizessupplied heat as a source of energy for adiscontinuous pumpingoperation.

A pumping system made according to the invention comprises a liquid linehaving valve-controlled'iinlet and outlet openings, and a heat-operatedpump connected into the line. The heat-operated pump is primarily a heatexchanger, one side of which is connected by two shunt lines to theliquid line and provided with a valvein at least one of these shuntlines, while the other side of the heat exchanger is connected to a heatsource. The heat supplied to this other side of the exchanger causessome of the liquid in the first side to boil, and the pressure of theresulting steam forces liquid from this first side through one of theshunt lines so as to displace liquid from the system through a one-wayValve against a counter-pressure. Thereafter, part or all of the steamis condensed while liquid enters the exchanger from the liquid line byway of the other shunt line, resulting in a pressure drop in the systemwhereby fresh liquid is sucked into it; and the pumping cycle isrepeated. The liquid is allowed to how in only one direction through theheat pump or exchanger, preferably by means of check valves in the twoshunt lines, although it may be sufiicient to provide only one of theselines with a valve.

According to a further feature of the invention, the heat-operatedpumping system also serves as an evaporator. In this case, a tank isarranged in the liquid line, and fresh liquid is supplied intermittentlyto the upper part of the tank through a pressure-controlled valve. Thelower part of the tank communicates with a valved opening through whichliquid is intermittently discharged from the system, and alsocommunicates with one of the shunt lines leading to the heat exchanger.The upper part of the tank is provided with a steam outlet containing apressure-operated valve and is connected with the other shunt lineleading from the heat exchanger.

For a better understanding of the invention, reference may be had to theaccompanying drawings in which The figure is a schematic view of oneform of the new heat-operated pumping system which serves also as anevaporator.

In the plate heat exchanger 1, the heating medium and the liquid to beheated are confined to thin layers as they flow through the exchanger,so that the heating of the liquid is effected as evenly and uniformly aspossible, without spotty over-heating. The plate heat exchanger 1 alsoprovide a large heat transfer area without requiring too much space.Also, the plate apparatus 1 may be of the well-known type which can bereadily opened for cleaning and inspection.

In the system shown in the figure, which also serves as an evaporator,the heat pump comprises a plate type of heat exchanger 1 formingpassages 1a and 1b for the liquid to be heated and the heating medium,respectively. The system also comprises a check valve 9a, a pressure a2,910,119 Patented Oct. 27, 1959 line 11a, a tank 12, a drop pipe 13 anda suction valve 511-. Periodic circulation through the system isobtained by supply of heat to the liquid in passages 1a of the plateapparatus l. The liquid is supplied to the system through a feed pipe14, which, together with the pressure pipe 11a for evaporated'liquid, isconnected to tank 12 (which may be a so-called cyclone) located at theupper part of the drop pipe 13. A discharge pipe'15 for the concentratedliquid is provided at the lower part of thedrop pipe 13. The plateapparatus 1 is provided with feed and discharge pipes .16, 1:7 for steamand condensate, respectively, communicating with passages 1b in theplate apparatus.

In the operation of the system of the figure, the liquid tobefevaporated is led into the tank 12 through the feed pipe 14; untilthe liquid level reaches a point directly below the opening 14 of thefeed pipe in the tank 12.

Heat is supplied to passages 1b of the heat exchanger,

preferably in the form of steam. The liquid in passages 1a then boilsinto steam, so-that the pressure in the space above the free liquidlevel'in'passages It: increases and the check valve 9a opens. The steamwith entrained liquid thus flows out into the tank 12, therebyincreasing the pressure in this tank. As a result, part of the steamwhich has entered tank 12 discharges through the valve 21 until, becauseof this escape of steam, a somewhat lower pressure has been attainedthan the steam pressure previously existing in the tank. At thissomewhat lower pressure, the valve 21 closes and the steam startscondensing in the tank 12 through contact with the tank wall and therelatively cold, free liquid surface in tank 12. As soon as the steamand entrained liquid have entered the tank .12, the liquid column intank 12 and in the drop pipe 13 is momentarily pressed down because ofthe relatively high steam pressure existing at this moment and alsobecause the liquid column in tank 12 now stands higher as a result ofthe entrained and transferred liquid than the liquid column in the plateheating apparatus 1, these columns tending to come into a state ofequilibrium. Consequently, the valves 5a and 18 open as a result of thepressure differential across them. Partially concentrated liquid of adesired concentration passes in part through check valve 18 and throughdischarge pipe 15; the remanider being returned to the system throughcheck valve 5a. The remainder of the liquid which is returned to thesystem is cool as compared to the liquid in the passages 1a, therebycooling the same and condensing steam in the spaces above the freeliquid level in the passages 1a in the heater. 7 The liquid spacesbetween the heat exchange plates are again substantially filled withliquid. Due to the resulting drop in the liquid level in tank 12 and theconsequent reduction in steam pressure in tank 12, which pressure isfurther reduced because the steam is condensed when contacting therelatively cold wall of tank 12 and the liquid surface in this tank,there is created in tank 12 an underpressure in relation to the pressureat the inlet opening 14, whereby the pressure responsive inlet valve 19opens so that fresh cold liquid is supplied to the tank .12 and theequilibrium is reestablished for the start of another pumping cycle.

By means of the steam escape from tank 12 through discharge pipe 20, themore readily evaporated component of the solution to be evaporated maythus discharge from the system.

The new apparatus may be used to especial advantage for evaporation ofmixtures in which at least one component is more volatile than the othercomponents and for-ms a solvent for them. Partially concentrated liquidis discharged through line 15 only after some period of operation of theapparatus, because during the first cycles of operation no partiallyconcentrated liquid can be sit- 3 uated in the lower part of drop pipe13. After a few cycles of operation, however, so much liquid has hadtime to circulate through the plate apparatus 1 that, during thefollowing pump strokes of the apparatus, part of the par-' tiallyconcentrated liquid is pumped into the plate apparatus 1 and part ispumped out through the line 15.

An advantage of the system of the figureis that the heat supplied to theplate apparatus, and which is necessary to evaporate the treated liquid,serves at the same time to circulate the liquid through the plateapparatus. The installation is thus economical and simple. It is notnecessary to install any circulation pump, which would demand thoroughattention in addition to great power consumption. To reduce as much aspossible the risk of burning-on in the plate apparatus, air included inthe treated liquid (such as milk and the like) may be evacuatedtherefrom before the liquid is fed to the evaporator.

I claim:

An evaporator system comprising a tank, a liquid conveying lineextending upward into the lower part of the tank, the tank having avalve-controlled inlet for the liquid, a heat exchanger of the .platetype having one side for a heating medium and a second side for liquidto be heated, a pipe line connecting the upper portion of said secondside of the heat exchanger to the upper portion of the tank, saidupwardly extending liquid conveying line having at its lower portion anextension leading to the lower portion of said second side of the heatexchanger, check valves in said pipe line and extension, respectively,for allowing liquid flow in only an upward direction through said secondside, a steam outlet pipe leading from the upper part of the tank, apressure valve in said steam outlet pipe, a liquid discharge lineleading from said extension at a point between the check valve thereinand the tank, and a check valve in said liquid discharge line.

References Cited in the file of this patent UNITED STATES PATENTS1,263,467 Reavell et al Apr. 23, 1918 1,846,307 Bush Feb. 23, 19321,848,226 Scott-Snell et al Mar. 8, 1932 2,015,240 Scott-Snell et a1.Sept. 24, 1935 FOREIGN PATENTS 715,012 Great Britain Sept. 8, 1954

